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Modeling velocity autocorrelation functions of confined fluids: A memory function approach

Krishnan, SH and Ayappa, KG (2003) Modeling velocity autocorrelation functions of confined fluids: A memory function approach. In: Journal of Chemical Physics, 118 (2). pp. 690-705.


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Velocity autocorrelation functions (VACF) of a fluid confined in a slit pore have been modeled using the memory equation. Models for the VACF are based on both the truncation and analytic closure approximations of the Mori's continued fraction representation. The performance of the models is evaluated for gas to liquid-like pore densities and pore widths which accommodate one to four atomic layers. In all cases we compare the predictions from the models with the VACF obtained from molecular dynamics simulations. The truncation models predict an oscillatory behavior for the in-plane VACF with better agreement at lower densities. Among the analytical closure models we observe that the sech model applied at the first level of closure is not only able to capture the short-time dynamics but is also seen to give the best predictions to the in-plane diffusivities at liquid-like pore densities. Although the minima in the VACFs are captured accurately by the sech model, the subsequent plateau regions in the VACF typically observed in confined systems are not predicted. This aspect is due to the slower relaxation of the actual memory kernel, which is not captured by the model. Predictions of the in-plane diffusivities using different levels of analytic closure have been compared with diffusivities obtained from the simulations.

Item Type: Journal Article
Publication: Journal of Chemical Physics
Publisher: American Institute of Physics
Additional Information: Copyright for this article belongs to American Institute of Physics (AIP).
Department/Centre: Division of Mechanical Sciences > Chemical Engineering
Date Deposited: 13 Jan 2005
Last Modified: 19 Sep 2010 04:17
URI: http://eprints.iisc.ac.in/id/eprint/2643

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